1. Field
The embodiment relates to a light emitting device, a method of fabricating the light emitting device, a light emitting device package, and a lighting system.
2. Background
A light emitting device includes a P-N junction diode having a characteristic of converting electrical energy into light energy. The light emitting device may include compound semiconductors belonging to group III and V on the periodic table. The light emitting device can represent various colors by adjusting the compositional ratio of the compound semiconductors.
When forward voltage is applied to the LED, electrons of an N layer are combined with holes of a P layer, so that energy corresponding to an energy gap between a conduction band and a valance band may be generated. The energy is mainly emitted in the form of heat or light. In the case of the LED, the energy is generated in the form of light.
For example, a nitride semiconductor represents superior thermal stability and wide bandgap energy so that the nitride semiconductor has been spotlighted in the field of optical devices and high-power electronic devices. In particular, blue, green, and UV light emitting devices employing the nitride semiconductor have already been commercialized and extensively used.
Recently, as the demand for the high-efficiency LED has been increased, the improvement of luminous intensity has been issued. According to the related art, as current is increased, a current crowding phenomenon occurs to lower light output power (Po), which is called “current crowding phenomenon”.
Accordingly, the requirements for the improvement in current spreading and luminous intensity are increased in order to overcome current crowding.
In addition, according to the related art, electrons (hot electrons) representing high mobility are not confined in a quantum well, but overflowed into the P type semiconductor layer, so that light emission efficiency is lowered.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.